Photographic tone correction mask



Jan. 4, 1944- R. H. MORRIS 2,338,661

PHOTOGRAPHIC TONE CORRECTION [ASK Filed Aug. 15, 1942 Robert H.M0rris INVENTOR WM BY mM Patented Jan. 4, 1944 UNITED STATES PATENT OFFICE PHOTOGRAPHIC TONE CORRECTION MASK Robert 11. Morris, Rochester, N. Y., assignor to Eastman Kodak Company, Rochester, N. Y., a

corporation of New Jersey Application August 15, 1942, Serial No. 454,933

12 Claims. (Cl. 95-2) This invention relates to a process in photography, and more particularly to a process in subtractive color photography whereby there is formed a tone correction mask which when placed in registry with a color transparency effects an improved tone reproduction curve for the transparency. I

In duplicating or printing transparencies, especially those obtained by the reversal process of subtractive color photography, onto a reversal material, the low contrast in the highlight regions is exaggerated by being printedonto the low contrast highlight regions oi. the reversal material.

Also, in printing from multicolored originals which consist in whole or in part of dyes, the fact that the light absorption of the dyes is exe tended to the whole spectrum rather than to one part of the spectrum makes it impossible to obtain printed records of the individual dyes simply by restricting the color of the printing light. Since in most three-color photographic processes the three dyes are not equally bad in this respect, the final result or printing such a film is to introduce unequal parts of all three records in each image which is made, regardless of the color of light used in printing or the sensitivity of the photographic materials used.

In order to compensate for the deficiencies of the dyes used in such processes, negative color correction masks are prepared by exposing a suitable sensitive emulsion layer through the multicolor originals with a selected exposing light and forming a metallic or colored image of the original in the exposed layer which, when placed in registry with the original during printing efiects color correction. Typical methods of preparing such masks are described in Evans U. S. Patent No. 2,203,653, granted June 4, 1940; Hanson U. S. Patent 2,294,981, granted September 8, 1942; Evans U. S. patent application Serial No. 413,442, filed October 3, 1941, and elsewhere.

In the present invention I describe a method of preparing a color. correction mask which not only corrects for the deficiencies oi the subtractive dyes of the color process, but also has tone reproduction characteristics such that when a print is made from the combination of the mask with the original transparency of which the mask is a record, large improvement in the final tone reproduction of the transparency is achieved in the print or duplicate.

One object of the present invention is to provide a tone correction mask. of use for improving tone reproduction during the printing of images halving improper tone reproduction characters cs.

One object of the present invention is to provide a tone correction mask of use in black-andwhite and color photography for improving tone reproduction during printing from black-andwhite or colored images having improper tone reproduction characteristics.

Another object of the present invention, and the preferred embodiment thereof, is to provide a tone and color correction mask of use in color photographyior improving the tone reproduction and color during printing from colored images.

In general, the objects of my invention are accomplished by forming in a photographic emulsion layer an image of opposite sign to a transparency having improper tone reproduction characteristics, of which it is a record, the characteristic curve of the image being such that when the image is combined with the transparency an improvement in tone reproduction is achieved.

In the figure of the accompanying drawing are shown by graphical representation the characteristic curves of various photographic elements employed in my invention.

In the figure oi the accompanying drawing, curve M represents the characteristic curve of an image obtained by low intensity exposure through a color transparency having a reproduction curve such as curve T. Curve M1 represents the characteristic curve of an image obtained by exposure through the transparency onto the unexposed area of the sam photographic element as contains-the image of curve M. Curve T1 represents the corrected reproduction curve of the transparency obtained when in printing, the image having curve M1 is used as a mask for the transparency having curve T.

My invention will now be described with particular reference to the accompanying drawing.

In a typical case to which my invention is particularly applicable, there is at hand a color transparency having a reproduction curve such as curve T of the drawing. In the normal process of reproducing this transparency, as for instance, onto a multicolor film by means of the reversal process of color photography employing color-forming development, there would be obtained a print in the toe region of which the low contrast of the toe of curve T would be exaggerated. This is true whether or not the usual color correction mask is employed in theprinting process. However, if in the manner of my invention another characteristic be imparted to the contrastemulsion of the type known in the art the mask is a positive in the shoulder region it may be said to have no density variations of opwhich, when exposed to light of one wave length,

gives high contrast, and exposed to light of another wave length gives low contrast, as for example, an emulsion disclosed in Carroll U. S. patent application, Serial No. 383,379, filed March 14, 1941, and having high contrast to blue light and low contrast to red light, is so exposed to the transparency of characteristics shown in curve -T through a blue filter (Wratten No. 47 filter) that substantially only those densities of the transparency below 0.6 are recorded. The film is then developed for about four minutes at 65 F. to a gamma of about 4 in a developing solution of the following composition:

Water, about 125 F cc 500 p-Methylamino-phenol sulfate grams 1.0 Sodium. sulfite, desiccated do 75.0 Hydroquinone do 9.0 Sodium carbonate, desiccated do 25.0 Potassium bromide do 5.0 Cold water to liter 1.0

Following development the film is washed and dried without fixing. The image contained therein has substantially the characteristics known by curve M of the drawing. For use with most color transparencies a gamma of the range of the order of 1 to 4 is satisfactory for this image.

The film is then placed in contact with the original transparency, or it may have originally been laminated thereto before exposure to eliminate registry problems, and again exposed through it, this time with red light (Wratten No. 25 filter). The exposure given is sufficient to recordlall of the detail of the transparency. Thereafter, film is developed to .a gamma of about 0.5 in a coupler developer of the following composition:

Diethyl p-pheneylene diamine grams 3 Sodium carbonate do 30 Sodium sulfite .do 6 p-Benzyl phenol do 3 Sodium hydroxide do 5 Water to liter 1 This developer deposits a gray image comprising an insoluble silver derivative insoluble in the usual solvents for removing silver from photographic elements such as ierricyanide-hypo solutions. Generally, a gamma of the range of the order of from 0.3 to 0.6 is satisfactory for this image, and the ratio of the gammas of this image to the gamma of the above high gamma image is, therefore, of the order of l/0.6 to 4/0.3. The higher the ratio selected the greater the correction imparted to the transparency. In addition,

instead of the above coupler-developing solution a is a low gamma image having density variations of opposite sign to the transparency having curve T, and the shoulder or high density region is a positive in respect to the transparency T. Since posite sign to the density variations of the transparency in that region.

In order to print color and tone corrected prints from the original transparency, the mask is placed inregistry with the transparency, prints being made on a suitable -multilayer color film in a process such as disclosed in Marines et al U. S. Patent 2,252,718, granted August 19, 1941, or if desired, color separationrecords may be printed and used in known color processes.

As shown by curve T1 of the drawing, the characteristic curve of the combination of the transparency and the mask is greatly improved. Not only has the mask effected an over-all decrease in contrast in the characteristic curve, but in the low density'region corresponding to the high-' light depends upon whether or what correction is desired but generally a light of longer wave length than blue is satisfactory, such as red, green, yellow, especially substantially monochromatic yellow light, chosen according to the principles laid down in the prior U. S. Patent 2,294,981 above-cited. In accordance with the principles of the Evans U. S. patent application, Serial No. 413,442 above-cited, the final mask may also be colored in respect to the color of the light exposing it as described therein. That is, instead of using the particular coupler developer above, another of the, well known color-forming developers giving a colored image may be used followed by the usual bleaching solutions for the silver images, fixing, washing, and drying.

In addition to the variable contrast emulsion given above, I may use in my invention other emulsions such as disclosed in the Carroll application above-cited; as, for example, one giving high contrast to green light and low contrast to red or yellow light. Similarly, other variable contrast emulsions are suitable for use in my invention. There is little use in my process, considering the dyes used at present in color photography, for a variable contrast emulsion giving high contrast to a region of the spectrum beyond blue and low contrast to the blue region of the spectrum. This is due to the fact that the tically the only case where a variable contrast emulsion of low contrast to blue light would be used is in case the color. process requires blue for the final exposure of the color correction mask.

In addition to the so-called variable contrast emulsions I may use for the masking emulsion layer an emulsion such as commonly used on posi tive motion picturefilm, that emulsions capable of development to a range of contrast of the order of 0.3 to 4 with different developing solutions. For example, in the manner of the process abovedescribed in detail, an emulsion highly sensitive to red, green, or yellow light is given a low intensity exposure through the transparency with, for example, blue light the sensitivity for the emulsion layer and the final exposing-light being chosen for the color correction desired, and de- In addition, my invention may be used in convelopment is carried out to a gamma of about 1 to 4 in a high contrast developing solution. Without fixing, the film is again Posed with the exposing light chosen for color-correction and developed in the low contrast coupler developer to a range of gamma of about 0.3 to 0.6.

The resultant image has the same characteristics as in the case where a variable contrast; emulsion was used and the two exposures were made with lights of different wave lengths.

As above-mentioned the mask or the invention having characteristics substantially as shown by curve M1, in order to compensate for low contrast in the highlight portion of a transparency, must have little or no gradation in the shoulder region, and may actually be a positive in the shoulder region in respect to the transparency. In curve M1 the mask is shown as having decreas-- ing density, i. 'e., positive density gradient in the shoulder region to compensate for the low contrast in the toe of the transparency curve T.

I contemplate as within my invention tone and color correction masks of the general characteristic described, wherein the straight line portion of the characteristic curve is negative in respect to a transparency of which it is a record, and in which in the shoulder region there is little or no gradation of opposite sign to the transparency, and including masks with density variations of the same sign in that region; Therefore, herein and in the appended claims where I state that the mask has in the shoulder region no appreciable density variations of opposite sign to the density variations of the transparency, I means it to be understood that this includes in the shoulder region (1) small density variations of opposite sign to the transparency but of an order less than normally obtained with photographic emulsions, 2) no density gradation in the portion of the shoulder masking the toe of the transparency, and

(3) density varying in the same direction as the density variations of the transparency.

Another use for which the mask of my invention is especially adapted, is in projecting or viewing of color transparencies. That is, in reversal processes of color photography where colored images are formed by means of color-forming development, images are obtained commonly having high contrast and the usual low contrast in the shoulder and toe regions. (See curve T.) A mask prepared as described is especially suitable for combining with such a transparency when it is desired to obtain the best image for viewing or projecting.

As is apparent, my invention i 'not limited to use in processes of color photography, however,

my preferred embodiment resides therein. That is, in processes of black-and-white photography when printing from transparencies having improper tone reproduction characteristics, as for instance, from a black-and-white image having lower gamma in the toe and shoulder regions of the characteristic curve than in the straight-line portion, a tone correction mask may be prepared which when used in prmting in combination with the image of which it is a record of opposite sign, an improvement in tone reproduction is obtained. In the past, practically the only method of improving tone reproduction in black-and-white photography has been to print an original transparency onto a process of different contrast thereby altering the overall contrast in the print but obtaining some compensation for errors in tone of the original.

junction with printing from a colored negative transparency, as for example, prepared from photographic elements deslgnedas described in Jelley and VittumjU. S. Patent 2,322,027, granted June 15, 1943; Mannes et al. U. S. Patents 2,304,939 and 2,304,940, granted December 15, 1942; that is, in conjunction with color films which after.

original exposure are immediately developed to subtractively colored dye images. In this case, the final mask is a, negative record of the color negative but, of course, is a positive in, respect to the final positive color print. In fact, my invention is applicable to the improvement of tone reproduction in any process of photography wherein the image of which the mask is a record has tone reproduction errors of the order described.

Also apparent. is the fact that the masks of my invention may be designed so as to correct not only for tone reproduction errors of the transparency being printed, but also to correct for tone reproduction errors introduced by the duplicating process. This is accomplished by giving the mask a shoulder gamma compensating for tone errors of both the toe of the transparency and any toe introduced in the duplicating process.

My invention having thus been described I would have it understood that the disclosure herein is by way of example, and that I consider as included in my invention all modifications and equivalents falling within the scope of the appended claims.

What I claim is:

1. The method of forming a photographic tone correction mask which comprises giving a lightsensltive silver halide photographic element an exphotographic element and of gamma lower than said silver image, and removing the high gamma silver image from the photographic element without afiecting said lower gamma image.

2. The method of forming a photographic tone correction mask which comprises giving a lightsensitive silver halide photographic element an exposure through a transparency of such intensity that only the toe densities of said transparency are recorded, developing in the exposed photographic element a silver image of opposite sign to said transparency and of suillciently higher gamma relative to a second image subsequently formed in the unexposed silver halide of the photographic element that said second image may he formed having characteristics such that when it is combined with said transparency an improvement in tone reproduction of the transparency is obtained, exposing the developed photographic elementcontaining said silver image and unexposed silver halide through said transparency to record all the detail of said transparency, forming in the re-exposed photographic element said image of lower gamma than said silver image and not attacked by solutions capable of removing silver from the photographic element, and removing the silver image from said photographic element without affecting said image of lower gamma.

3. The method of forming a photographic tone and color correction mask which comprises giving a light-sensitive silver halide photographic element an exposure through a color transparency of such intensity that only the toe densities of said transparency are recorded, developing in the exposed photographic element a silver image of opposite sign to said transparency and of suffi ciently higher gamma relative to a second image subsequently formed in the unexposed silver halide of the photographic element that said secnd image may be formed having characteristics v .graphic element said image of lower gamma than said silver image and not attacked by solutions capable of removing silver from the photographic e1- ement, and removing the. silver from said photographic element without affecting said image of lower gamma.

4. The method of forming a photographic tone and color correction mask which comprises giving a light-sensitive silver halide emulsion layer an exposure through a color transparency of such intensity that only the toe densities of said transparency .are recorded, developing in said exposed layer with a high gamma developing solution a silver image of opposite sign to said transparency and of higher gamma relative to a second image subsequently formed therein, xposing the developed layer containing said silver image and unexposed silver halide through said transparency to record all the detail of said transparency with light of wave length affording the desired color correction, developing in the re-exposed photographic layer with a low gamma developing solution an image not attacked by solutions capable of removing silver from'said layer and of gamma less than said silver image, and removing said higher gamma silver image.

5. Ihe'method of forming a photographic tone and color correction mask which comprises giving a light sensitive silver halide emulsion layer capable of development to a gamma of a range of the order of from 0.3 to 4 an exposure through a color transparency of suchintensity that only the toe densities of said transparency are recorded, developing in said exposed layer with a high gamma developing solution a silver image of opposite sign to said transparency and of higher gamma relative to a second image subsequently formed therein, exposing the developed layer containing said silver image and unexposed silver halide through said transparency to record all the detail of said transparencywith light of wavelengths afiording thedesired color correction, developing in the re-exposed photographic layer with a low gamma developing solution an image not attacked by solutions capable of removing silver from said layer and of gamma less than said silver image, and removing said high gamma silver image, the gamma of said higher gamma silver image being of the range of the order of 1 to 4 and the gamma of said lower gamma image being of the range of the order of 0.3 to 0.6.

6. The method of forming a, photographic tone correction mask which comprises giving a light element a silver image of opposite sign to said transparency and of higher gamma than a second image subsequently formed therein, exposing the developed photographic element containing said silver image and unexposed silver halide through said transparency to record all the detail of said transparency with Wave lengths of exposing light such that a low gamma image may be formed therein, forming in the i e-exposed photographic element an image not attacked by solutions capable Of removing silver from the photograpluc element, and removing the higher gamma image from the photographic element Without affecting said lower gamma image. i

'7. The method of forming a photographic tone and color correction mask which comprises giving a light-sensitive variable contrast silver halide photographic element an exposure through a color transparency of such intensity that only the toe densities of said transparency are recorded with wave lengths of exposing light such that the photographic element may be developed to a high gamma, developin in the exposed photographic element a, silver image of opposite sign to said transparency and Of higher gamma than a second image subsequently formed therein, exposin the developed photographic element containing said silver image and unexposed silver halidethrough said transparency to record all the detail of said transparency with wave lengths of exposing light such that a low gamma image may be formed therein, forming in the re-exposed photographic element an image not attacked by solutions capable of removing silver from the photographic element, and removing the higher gamma image from the photographic element without affecting said lower gamma image, the gamma of said higher gamma silver image being of the range of the order of 1 to 4 and the gamma of said lower posite sign to said transparency and of higher gamma than a second image subsequently formed therein, exposing the developed photographic element containing said silver image and unexposed silver halide through said transparencyto record all the detail 01E said transparency with a wave length of exposing light such that a low gamma image may be formed therein, forming in the reexposed photographic element an image not attacked by solutions capable of removing silver from the photographic element, and removing the higher gamma image from the photographic element without affecting said lower gamma image, said lower gamma image being of opposite sign to said transparency in the straight-line portion of its characteristic curve and of the same sign 2,sss,ec1

as said transparency in the shoulder portion of its characteristic curve.

9. The method of forming a photographic tone and color correction mask which comprises givin a' light-sensltive silver halide photographic element of highcontrast to blue light and low contrast to red light a blue light exposure through a positive color transparency of such intensity that only the toe densities of said transparency are recorded, developing in the exposed photographic element a silver image of opposite sign to said transparency and of higher gamma than a second image subsequently formed therein, exposing the developed photographic element containing said silver image and unexposed silver halide through said transparency with red light to record all the detail of said transparency, forming in the re-exposed photographic element an image not attacked by solutions capable of removing silver from the photographic element and of gamma lower than said silver image, and removing the higher gamma image from the photographic element without affecting said lower gamma image. said lower gamma image being of opposite sign to said transparency in the straightline portion of its characteristic curve and of the same sign as said transparency in the shoulder portion or its characteristic curve.

10. The method of forming a photographic tone color correction mask which comprises giving a light-sensitive silver halide photographic element oihigh contrast to green light and low contrast to yellow light a green light exposure through a positive color transparency of such intensitythat only the toe densities oi said transparency are recorded, developing in the exposed photographic element a silver image oi opposite sign to said transparency and of higher gamma than a second image subsequently iorme therein, exposing the developed photographic element containing said silver image and unexposed silver halide through said transparency with yellow 11. The method of forming a photographic tone and color correction mask which comprises giving a light-sensitive variable contrast silver halide photographic element an exposure through a negative color transparency of such intensity that only the toe densities of said transparency are recorded with a wave length of exposing light such that the photographic element may be developed to a high gamma, developing in the exposed photographic element a silver image of opposite sign to said transparency and a higher gamma than a second image subsequently formed therein, exposing the developed photographic element containing said silver image and unexposed silver halide through said transparency to record all the detail of said transparency with a wave length of exposing light such that a low gamma image may be formeci therein, forming in the re-exposed photographic element an image not attacked by solutions capable of removing silver from the photographic element, and removing the higher gamma image from the photographic element without aflecting said lower gamma. image,

said lower gamma image being of opposite sign to said transparency in the straight line portion of its characteristic curve and of the same sign as said transparency in the shoulder portion of its characteristic curve.

12. The method of forming a photographic tone and color correction mask which comprises giving a light-sensitive silver halide photographic element of high contrast to green light and low contrast to red light a green light exposure through a negative color transparency of such intensity 1 that only the toe densities of said transparency are recorded, developing in the exposed photographic element a silver image of opposite sign light to record all the detail of said transparency,

forming in the re-exposed photographic element an image not attacked by solutions'capable of removing silver irom the photographic element and oi gamma lower than said silver image, and removing the higher gamma image rrom the photographic element without aiiecting said lower gamma image, said lower gamma image being or opposite sign to said transparency in a straight line portion of its characteristic curve and oi thesame sign as said transparency in the shoulder portion oi this characteristic curve.

to said transparency and of higher gamma than a second image subsequently formed therein, exposing the developed photographic element containing said silver image and unexposed silver halide through said transparency with red light to record all the detail of said transparency,

I forming in the re-exposed photographic element an image not attacked by solutibns capable of removing silver from the photographic element and of gamma lower than said silver image, and

removing the higher gamma image from the photographic element without aflecting said lower gamma image, the gamma of said higher gamma image being of the range of the order of 1 to 4 and the gamma oi said lower gamma image being of the range or the order of 0.3 to 0.6. ROBERT H. MORRIS. 

